2007 Annual Report 1a.Objectives (from AD-416) To develop new or improved methods for hydroponic and greenhouse crop production and greenhouse disease and pest management; to clone geranium (Pelargonium spp.) genes involved in post-transcriptional gene silencing (PTGS) to boron and silicon; and to develop a consistent mechanical inoculation method for infecting geranium (Pelargonium spp.) with Tobacco ringspot viruses (TRSV) and Tomato ringspot viruses (ToRSV) present in several accessions derived from the Ornamental Plant Germplasm Center, Columbus, OH. 1b.Approach (from AD-416) A joint research project on Hydroponic and Soilless Culture was initiated between the USDA, ARS and the University of Toledo. Proper management of insect and disease will enhance profitability and competitiveness of American growers. USDA, ARS will hire a Research Horticulturist and a Research Plant Pathologist to be located at the University of Toledo as an ARS Worksite of the USDA, ARS, Application Technology Research Unit in Wooster. Virus diseases of Pelargonium spp. are relatively common but different to assess because the host is usually not killed by infection. Develop a consistent mechanical inoculation method. Infect plants with TRSV and ToRSV and expose to varying concentrations of boron and silicon to determine their effects on viral disease and virus titers will be examined by serology and RT-PCR. The effects of photoperiod and temperature on virus infection will be examined in a similar manner. Since it may take some time to develop a consistent method of mechanical inoculation with TRSV and ToRSV in Pelargonium species, it would be advantageous to use plant material that is already infected. However, it would be important to first find out what viruses are present within these infected plants. At least two of the accessions obtained from the Ornamental Plant Germplasm Center are apparently infected with a ringspot virus. Therefore, we will need to characterize these viruses. This will be done by electron microscopy, serological techniques, and RT-PCR. Cuttings would be propagated from this previusly infected material and exposed to different nutrient and environmental conditions and their effects on virus infection would be analyzed as described above. 3.Progress Report This report documents research conducted under a Specific Cooperative Agreement between ARS and the University of Toledo. Additional details of the research can be found in the report for the parent project 3607-21000-011-00D Develop Improved Technologies for Soilless Greenhouse Plant Production to Minimize Water, Labor, Agrochemical Inputs and Environmental Impacts. The effects of nutrition and environment on viral infections are poorly understood, especially as related to virus diseases of ornamental plants. Most of the individual genes for Pelargonium flower break virus (PFBV) and Pelargonium line pattern virus (PLPV) have been cloned and are being inserted into two yeast two-hybrid vectors to be used in studying interactions among the viral proteins. This effort may help to develop potential resistance in Pelargoniums. A RT-PCR technique has been developed to detect tobacco ringspot virus in both Pelargonium and zinnia which allows quantitative comparison of levels of both RNAs in a variety of hosts. In silicon nutritional studies, it was discovered that expression of genes encoding for copper transporters declines with the addition of silicon, possibly explaining the benefit of silicon in alleviating copper toxicity. These studies are likely to lead to a novel understanding of virus-host-environment interactions. These accomplishments address NP-305, Component I, Problem Statement C. 4.Accomplishments Virus infection of Pelargonium species is problematic. Viruses induce a variety of symptoms, reducing the ability of plants to grow well and increasing their susceptibility to other pathogens. In addition, viruses can damage flowers, causing death of buds, distortion of flowers or a reduction of flower number. This is often a hidden problem because there are many cases where infected plants do not show symptoms until they flower and by then it is too late. Finally, Pelargonium is a difficult system in which to apply molecular biology techniques. It would be most useful to develop a model system to study Pelargonium viruses and then transfer the technology to Pelargonium. That has been part of our goal for over a year now. Our first task was to determine just what viruses are associated with Pelargonium infection since much of the information regarding this is somewhat out-of-date. In a survey of Pelargonium species from the Ornamental Plant Germplasm Center (Columbus, OH), we discovered that two viruses were the most prevalent: Pelargonium flower break virus (PFBV) and Pelargonium line pattern virus (PLPV). Both viruses were found either alone or in co-infections and both are related, being from the same virus family. We have recently shown that PLPV can be transmitted to the model plant Arabidopsis thaliana. This will greatly accelerate our work because PLPV symptoms appear in Arabidopsis thaliana in about three weeks, while they can take months to years to show up in Pelargonium. This SCA is focused on nutritional effects on virus infection. The rapid formation of symptoms will permit us to examine the effects of element (e.g., B and Si) deficiency and excess on resistance to PLPV without having to wait for an excessive amount of time. Furthermore, many molecular tools are available in A. thaliana that are not available for many other plants. Therefore, we can test the effects of specific genes on PLPV infection in A. thaliana and extend that work to Pelargonium. This is why, for example, we have recently isolated a Pelargonium gene implicated in virus resistance in other plants. We can also generate transgenic Arabidopsis fairly quickly as well, so we can test the impact of certain transgenes on PLPV infection in that host and extend that work to Pelargonium as well. Overall, this discovery will greatly benefit the floriculture industry by providing a new understanding of Pelargonium viruses and generating new strategies for defense against these pathogens. This accomplishment addresses the NP-305 components "Integrated Production Systems" and Agroengineering, Agrochemical, and Related Technology", and NP-303 "Plant Diseases". 5.Significant Activities that Support Special Target Populations None. 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 2 Number of newspaper articles and other presentations for non-science audiences 2